The present invention is a method and apparatus for hydraulically disengaging an output shaft of a hydraulic motor. In particular, the hydraulic motor includes a longitudinal movable output shaft which may be moved hydraulically for allowing the driven mechanism to rotate without interference from the hydraulic motor.
In hydraulic equipment, and especially mobile hydraulic equipment, it is often necessary and/or desirable to disengage the hydraulic motor from the mechanism it is driving so as to free wheel the mechanism. An example of this is a hydraulic motor which is connected to the wheels of a mining machine and used to propel the mining machine. When it becomes necessary to tow the mining machine the hydraulic motor must be disengaged from the drive train so the machine will roll freely. Another example is a scissor-lift used to load and unload aircraft. It is typically driven with a hydraulic motor connected to its drive train. When this vehicle requires towing, it is again necessary to disengage the motor from the drive train. Another example is a knuckle-boom loader which is used in the harvesting of timber. When it is in the woods, it is propelled by a hydraulic motor connected to its drive train. When it is transported to another job site, the hydraulic motor must be disconnected to allow the knuckle-boom loader to be towed.
Yet still another example is when a hydraulic motor is used to drive a winch. It is often necessary to disengage the motor in order to free wheel cable off the winch. Disengaging the hydraulic motor in the above examples is often accomplished by unbolting and physically removing the motor, building an elaborate slide which will slide the motor out of engagement, or using an expensive clutch between the motor and the drive train which can disengage the motor. Such disengagement may also be accomplished by hand, as set forth in U.S. Pat. No. 5,261,801. However, the art lacks a means of hydraulically engaging and disengaging a hydraulic motor.